Edoardo Peronace

Low slip rates and multimillennial return times for Mw 7 earthquake faults in southern Calabria (Italy)

The Calabrian Arc is the epicentral region of one third of the strongest earthquakes of Italy (Mw ≥ 7.0). These are confined within a narrow peninsula which is the emerging portion of a slab-related accretionary wedge, and all occurred in the past four centuries. Therefore, here more than anywhere in Italy, historical seismicity alone is not sufficient for seismic hazard assessment. We carried out geological and paleoseismological studies in southern Calabria that allowed characterizing the seismogenic behavior of the Cittanova fault which was responsible for one of the most catastrophic earthquakes to ever occur in Europe, the Mw 7.0 5 February 1783 event. We have found out conclusive evidence for four Holocene earthquakes prior to 1783, with a recurrence time longer (~3.2 kyr) than the other Apennine faults (0.3–2.4 kyr). We have also estimated a robust slip rate for the late Upper Pleistocene (0.6 mm/yr) and an extension rate (0.4 mm/yr) that could reflect the residual back-arc opening of the Tyrrhenian Basin.

Testing geomorphic signal of active normal faulting: The case of the Cittanova Fault (Calabria, southern Italy): Testing geomorphic signal of active normal faulting (Cittanova Fault)

Extracting tectonic signals from the landscape is an important challenge for constraining the style and rate of deformation associated with active faults, especially where their displacement history cannot be independently determined. Based on previous paleoseismological data coupled with new geomorphological field work and C dating of geomorphic markers, we analysed the geomorphic signal of the along-strike differential throw of the Cittanova Fault in southern Calabria (Italy), the recent activity of which is already well documented and constrained. Through DTM-derived stream power law parameters (SL and χ), we provide evidence of drainage network disequilibrium and reorganization in response to fault growth and deformation style. Furthermore, a methodological test of the reliability of the χmetric as a proxy for the differential throw along the strike of active normal faults provided good preliminary results, consistent with a strong inverse linear correlation with fault throw. Copyright

On the Performances of Site Parameters for Soil Classification

The selection of specific elastic response spectra according to soil categories is the standard to account for site effects in engineering design and general-purpose hazard maps. Most of the international seismic codes are based on the average shear wave velocity of the upper 30 m (Vs30) to discriminate between soil categories. The works of Borcherdt and Glassmoyer (1992) and Borcherdt (1994) were the first to propose the adoption of the VS30 as a tool to discriminate soils with similar seismic response. Nevertheless, after Borcherdt (1994), some doubts arose about the capability of Vs30 in site effects estimation (among others, Steidl 2000; Park and Hashash 2004; Stewart et al. 2003; Castellaro et al. 2008; Lee and Trifunac 2010). The objectives of this study are: (i) to find soil classes with a similar response to an earthquake; (ii) to develop empirical amplification factors for 5 % damped response spectral acceleration in the period range T 0.04–4 s; (iii) to identify proxies for site classification (Vs30, stratigraphy, fundamental frequency, etc.). We propose a soil classification, which is not based on a priori subdivision, but it relies on the natural aggregation of empirical amplification function of the sites, obtained by normalizing the spectra of recorded motions by a reference (rock) spectrum from a ground motion prediction equation (GMPE, developed by Bindi et al. 2011, based on the ITACA 1.0 database). The empirical amplification functions of sites are aggregated by means of cluster analysis.